Plasma leptin concentrations in obese children: changes during 4-mo periods with and without physical training

Background: Little is known about the effects of physical training on plasm a leptin concentrations in children. Objective: We sought to determine the effects of 4-mo periods with and with out physical training on leptin in obese children and to explore the determ inants of leptin at baseline and in response to physical training. Design: participants were 34 obese 7-11-y-old children randomly assigned to engage in physical training during either the first or second 4 mo of the 8-mo study. Results: Total body composition, visceral adiposity, and insulin were all p ositively correlated with leptin at baseline (P less than or equal to 0.05) : however, only fat mass was retained in the final stepwise regression (P = 0.0001, R-2 = 0.57). Leptin decreased during the 4-mo periods of physical training and increased in the 4 mo after cessation of physical training (P < 0.001 for the time by group interaction). Decreases in leptin were greate st in children with higher pretraining leptin concentrations, those whose t otal mass increased least, and those whose insulin concentrations decreased most (P less than or equal to 0.05); only pretraining leptin concentration (P = 0.009) and change in total mass (P = 0.0002) were retained in the fin al regression (R-2 = 0.53). Conclusions: In obese children, leptin concentration decreased during 4 mo of physical training and increased during a subsequent 4-mo period without physical training, fat mass was highly correlated with baseline leptin, and greater reductions in leptin during 4 mo of physical training were seen in children with higher pretraining leptin and in those whose total mass incr eased least.